Method and apparatus for communicating protocol data unit in a radio access network

ABSTRACT

A new protocol data unit is used in communications in a radio access network. When a user equipment requests a radio resource controller connection, the UE includes its identity in the request message. In establishing the connection to UE, a serving radio network controller allocates a logical channel to the UE for communications and identifies the logical channel in the header of the protocol data unit so as to allow a receiver of the PDU to know the UE identity in an out-of-band signaling fashion, depending upon a state of the transmitter of the PDU. When the transmitter changes its state, the receiver can change state accordingly. The new PDU structure allows continuous reception of the HS-DSCH downlink channel during state transition form CELL_FACH or CELL_PCH or URA_PCH to CELL_DCH and vice versa. This new PDU structure also allows continuous HS_DSCH retransmissions.

This application claims priority to co-pending U.S. Patent ApplicationsNo. 60/852,331, filed Oct. 16, 2006, and No. 60/852,606, filed Oct. 17,2006.

FIELD OF THE INVENTION

The present invention relates generally to the downlink transmission ina Universal Mobile Telecommunications System (UMTS) Terrestrial RadioAccess Network (UTRAN) or long term evolutions of UTRAN and, moreparticularly, to the UTRAN high speed downlink packet access (HSDPA)operation in CELL_FACH (forward access channel) state.

BACKGROUND OF THE INVENTION

As is known in the field, a further development of the wideband codedivision multiple access (WCDMA)/universal mobile telecommunicationssystem (UMTS) communication system is the definition of the system knownas high speed downlink packet access (HSDPA). HSDPA operates as atime-shared communications channel which provides the potential for highpeak data rates as well as the possibility for having a high spectralefficiency. HSDPA improves system capacity and increases user data ratesin the downlink, that is, for transmission of data from a radio basestation (BTS) to a user equipment (UE). BTS is also known as a Node Bserver in a UMTS system.

FIG. 1 illustrates a prior art radio interface protocol structure ofHSDPA. It shows the relationship between the different layers among UE,Node B and various radio network controllers (RNCs). In FIG. 1, RLC isthe radio link control layer, and MAC is the medium access control layerand PHY is the physical layer. MAC-hs (MAC high-speed) is a new MACentity terminated in Node B for controlling the HS-DSCH transport layer.MAC-c (common MAC) is an entity in the UE, which transfers MAC-c PDU(protocol data unit) to the peer MAC-c entity in the RNC using theservices of the physical layer. MAC-c/sh is responsible for the PCH(Paging Channel), FACH (Forward Access Channel), DSCH (Downlink SharedChannel) and RACH (Random Access Channel). MAC-d (dedicated MAC) isresponsible for dedicated channels (DCHs) and is retained in the servingRNC, whereas MAC-c/sh is in the controlling RNC. L1, L2 are radioresources for the radio resource controller connection. L1 is a physicallayer and L2 is a data link layer.

An HS-DSCH channel is a downlink transport channel shared by severalUEs. The HS-DSCH is associated with one downlink DPCH (downlinkdedicated physical channel) or F-DPCH per active user, and one orseveral shared control channels (HS-SCCH). The HS-DSCH can betransmitted over the entire cell or over only part of the cell usingbeam-forming antennas, for example.

In terms of channels, there are three types of UMTS channel levels in aUMTS system so as to allow a UE to communicate with other networkcomponents: physical channels, transport channels and logical channels.The logical channels provide transport bears for information exchangebetween MAC protocol and RLC protocol. Transport channels provide thebearers for information between MAC protocol and the physical layer.Physical channels, which are identified by frequencies, spreading codes,etc., provide the transport bearers for different transport channels.

The logical channel can be used for communicating a PDU to or from a UEin a radio access network. Among various fields in the PDU, one is usedto identify the UE (UE-id) and one is used to indicate the UE-id type.Most of the control signaling between UE and UTRAN is Radio ResourceControl (RRC) messages. When the serving radio network controller(S-RNC) establishes the radio resource control (RRC) connection to a UEand decides to use a dedicated channel for this particular RRCconnection, it allocates a UTRAN radio network temporary identity (RNTI)and radio resources L1, L2 for the RRC connection. An RRC connection setup message is sent from the S-RNC to the UE. It is known that UE has twobasic operation modes, the Idle Mode and Connection Mode. The transitionfrom the Idle Mode to the UTRAN Connection Mode is initiated by the UEby transmitting a request for RRC connection. When the UE receives amessage from the network confirming the establishment of the RRCconnection, the UE enters the CELL_FACH (forward access channel) stateor CELL_DCH (dedicated channel) state of the UTRAN Connection Mode.

Although HSDPA is an efficient method for delivering relatively largeamounts of data in relatively small time periods (the transmission timeinterval, or TTI, for a HSDPA system is 2 ms). This performance,however, can only be used when the user equipment is operating withinthe dedicated channel state (CELL_DCH state). In other words, theperformance can be carried out only after a physical layer connectionbetween UE and the BTS has been established and the layer connection hasdedicated channels allocated to it. The transition from the UE Idlestate to the dedicated channel state (CELL_DCH state) and establishingan HSDPA connection may take up to a second. When the amount of datarequired to be transmitted is relatively small, the state transition tothe CELL_DCH state can take longer than the actual data transmission.

Moreover, when the UE is in the process of changing states to theCELL_DCH state, the required state change has to be addressed to the UEby the forward access channel (FACH). This required state change issignificantly slower and less robust than the later HSDPA transmissionchannels. Before and during the transition to the CELL_DCH state, theCELL_FACH state requires that both the downlink dedicated controlchannel (DCCH) and the downlink dedicated traffic channel (DTCH) aremapped onto the forward access channel (FACH).

To avoid data loss during state transition between CELL_FACH state andCELL-DCH state, even when HSDPA MiMo (multiple-input multiple-output fortransmit/receive diversity) is used, it is possible to stop downlinkdata transmission for certain time as the network is not aware of theexact time instance when UE is able to operate in CELL_DCH state andreceive a correct downlink channel and the PDU format. In particular, itis possible to directly map MAC-d PDUs to MAC-c PDU as defined in Rel99and then to map MAC-c PDU to MAC-hs PDU as shown in FIG. 2 a(multiplexing structure) and FIG. 2 b (PDU header structure).

In a non-HS-DSCH channel, a MAC PDU has a MAC header section and a MACSDU (Service Data Unit) section. The MAC header section has four fields:a Coding of Target Channel Type Field (TCTF), a UE-id Type field, aUE-id (UE identity) field and a C/T field. The C/T field is used toprovide identification of the logical channel instance when multiplelogical channels are carried on the same transport channel. The TCTFfield is used to provide identification of the logical channel class onFACH and RACH transport channels. The C/T field is also used to provideidentification of the logical channel type on dedicated transportchannels on FACH and RACH when used for user data transmission.

In a MAC-hs PDU consists of one MAC-hs header and one or more MAC-hsSDUs (Service Data Units). A maximum of one MAC has PDU can betransmitted in a TTI per UE. The MAC-hs header is of variable size. TheMAC-hs PDU in one TTI (Transmission Time Interval) belongs to the samereordering queue. TTI indicates how often data arrives from higherlayers to the physical layer. As shown in FIG. 2 b, the MAC-hs headerincludes a priority Queue ID to identify a priority level of the MAC-dflow, a transmission sequence number (TSN) and one or more groups ofthree fields (SID, N and F), wherein SID (Size Index) indicates thelength of each SDU, N indicates the number of SDUs having the length ofthe SID, and F (Flag) indicates whether the next field contains the SIDlength information. Thus, the group or groups of SID, N and F areindicative of the number or size of one or more subsequent protocol dataunits. Queue ID is also indicative of the reordering queue in thereceiver. In addition, in front of the MAC-hs header, a version flag(VF) is also provided.

In the above-described multiplexing scheme using the PDU structure, thetransition from the UE to the dedicated channel state (CELL_DCH state)and establishing an HSDPA connection may take more time than the actualdata transmission, especially when the amount of data required to betransmitted is relatively small. The PDU structure as shown above can befurther improved.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for communicatinga protocol data unit (PDU) between a user equipment device and anothernetwork component over a logical channel in a radio access network,using a different PDU structure. In a scenario when a user equipmentsends a request message to a serving radio network controller (SRNC)requesting a radio resource controller (RRC) connection, the userequipment includes its identity (UE-id) in the request message. Inestablishing the RRC connection to UE, SRNC allocates a radio networktemporary identity and radio resources for the connection and sends anRRC set up message to UE, including a coded UE identity as part of theRRC message. Additional scenario where UE ID could be updated are whenUE sends Cell Update or URA Update message to the network (NW) andnetwork sends Cell Update Confirm message back to the UE. Furthermore,in the scenario where the UE is having all necessary ID allocated, thePDUs can be transmitted between UE and NW via common channels so that UEidentity needs to be encompassed in each transmission.

As such, the identity of a user equipment can be indicated inout-of-band signaling. This out-of-band signaling is used in a format ofthe PDU known to the network component receiving the PDU. The networkcomponent receiving the PDU knows which identity is used in theout-of-band signaling depending upon a state of the network component.When the network component transmitting the PDU has changed from onestate to another, the out-of-band signaling allows the network componentreceiving the PDU to know the state change, so that the receiver changesthe state if the transmitter has changed the state.

The present invention uses a new PDU structure to transfer data andsignaling to the user equipment in the Idle state or in the UTRANconnected states (CELL_DCH, CELL_FACH, CELL_PCH or URA_PCH). As it isknown in the art, the transition from the Idle Mode to the UTRANConnection Mode is initiated by the UE by transmitting a request for RRCconnection. When the UE receives a message from the network confirmingthe establishment of the RRC connection, the UE enters the CELL_FACH(forward access channel) state and CELL_DCH (dedicated channel) state ofthe UTRAN Connection Mode. The new PDU structure is used in bothCELL_FACH and CELL_DCH states when HS-DSCH reception is enabled in thosestates. Furthermore, the new PDU structure is used as a singlemultiplexing layer for multiplexing different logical channels to anHS-DSCH transport channel.

One improvement regarding the PDU structure change, according to thepresent invention, is to allow continuous reception (without breaks inconsecutive TTIs) of the HS-DSCH downlink channel during the statetransition from CELL_FACH or CELL_PCH or URA_PCH (for UTRAN RegistrationArea) to CELL_DCH or vice versa.

One improvement regarding the PDU structure change, according to thepresent invention, is to allow HS-DSCH HARQ retransmissions to continueduring the state transition from CELL_FACH to CELL_DCH or vice versa.This is possible as PDU structure in both states is identical and, fromreceiver point of view, there is no difference if some first HARQtransmission occurred in a different state than the last HARQtransmission when the PDU were able to be decoded correctly.

One improvement regarding the PDU structure change, according to thepresent invention, is to allow a variable MAC-hs SDU size by utilizingthe length field.

One improvement regarding the PDU structure change, according to thepresent invention, MAC-hs segmentation and concatenation in CELL_DCH andCELL_FACH states. The segmentation is achieved by utilizing the lengthand SC fields and concatenation is achieved by repeating the headerfields.

One improvement regarding the PDU structure change, according to thepresent invention, is to avoid length indicators in RLC to indicate SDUboarders. This is achieved by using last field in the RLC header toindicate the end of the SDU. The RLC header has a last segment flag (L)to indicate the last segment, a polling bit (P) to indicate a statusreport is required, and a D/C field to indicate whether the PDU is acontrol PDU or an AM PDU. It should be also noted that actual order ofthe different fields in MAC-hs protocol header not essential for thisinvention.

One improvement regarding the PDU structure change, according to thepresent invention, is to reduce the overall L2 overhead introduced byRLC and MAC layers in CELL_FACH, CELL_PCH, URA_PCH and CELL_DCH state.

One improvement regarding the PDU structure change, according to thepresent invention, is to introduce fully octet aligned L2 protocolheaders for RLC and MAC layers in CELL_FACH, CELL_PCH, URA_PCH andCELL_DCH state to reduce L2 processing in high speed data connections.

Other aspects of the PDU structure change, according to the presentinvention, include the removal of the TCTF, UE-id type and UE-id fieldsfrom the MAC-hs header; the replacement of the Queue ID field in theMAC-hs header by a Logical channel ID field, the replacement of the SID,N1 and F1 fields by Length field and SC field. Moreover, the MAC-dmultiplexing and the MAC-c multiplexing are avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the radio interface protocol architecture of HSPDA.

FIGS. 2 a and 2 b illustrate the multiplexing and L2 PDU structure basedon Rel99 definitions.

FIGS. 3 a and 3 b illustrate the multiplexing and L2 PDU structure basedon a format, according to the present invention.

FIGS. 4 a to 4 e show different PDU structures for different logicalchannels, according to the present invention.

FIG. 5 a shows an AMD-RLC and MAC-hs header structure, with a 3 octetMAC-hs header structure, according to the present invention.

FIG. 5 b shows an AMD-RLC and MAC-hs header structure, with a 4 octetMAC-hs header structure, according to the present invention.

FIGS. 6 a to 6 c show a radio access network having a plurality ofnetwork components using the PDU structure, according to the presentinvention.

FIG. 7 a shows an apparatus in the radio access network configured toreceive and process the PDU, according to various embodiments of thepresent invention.

FIG. 7 b shows an apparatus in the radio access network configured forimplementing the PDU, according to various embodiments of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is concerned mainly with the uplink transmissionin a Universal Mobile Telecommunications System (UMTS) Terrestrial RadioAccess Network (UTRAN) or long term evolutions of UTRAN and, moreparticularly, to the UTRAN high speed downlink packet access (HSDPA)operation in CELL_FACH (forward access channel) state and flexible RLCsize and MAC-hs segmentation in CELL_DCH state. The present inventionprovides a new PDU structure for the communications between one networkcomponent of a radio access network to another network component. Thepresent invention also provides a method for communicating the new PDUto or from a user equipment (UE) in the radio access network.

When the serving radio network controller (SRNC) establishes the radioresource controller (RRC) connection to a UE and decides to use adedicated channel for this particular RRC connection, it allocates aUTRAN radio network temporary identity (RNTI) and radio resources L1, L2for the RRC connection. An RRC connection set up message is sent fromthe S-RNC to the UE. The RRC connection set up message contains thepermanent UE identity that the UE includes in the RRC Connection Requestmessage and the MAC-hs PDU format as shown in FIG. 4 a. This UE identityis coded as part of RRC message and not present in MAC PDU. When the RRCconnection is established, the UTRAN assigns the U-RNTI, C-RNTI andH-RNTI identifiers to the UE. The U-RNTI is valid inside UTRAN inCELL_FACH state and in CELL/URA_PCH state and the C-RNTI is valid insidethe cell in CELL_FACH state. Here URA denotes a UTRAN registration area.In HSDPA operation in CELL_DCH state, each UE is assigned a uniqueH-RNTI that is used to identify the intended receiver of eachtransmitted packet already in the physical layer. In operation, all RRCmessages are exchanged between a terminal and the RNC through thesignaling radio bearers (SRBs). SRB characteristics are determined basedon the mode of operation of the RLC and the type of logical channelused. A common control channel (CCCH) and dedicated control channel(DCCH) are used for the SRBs. Among the SRBs, SRB#0 is used for theuplink (UL) with the RLC layer operating in a transparent mode (TM) orfor the downlink (DL) with the RLC layer operating in a unacknowledgedmode (UM). The logical channel for SRB#0 is CCCH. With SRB#1, the RLClayer is operating in the UM and the logical channel is DCCH. With SRB#2through SRB#4, the RLC layer is operating in an acknowledged mode (AM)and the logical channel is DCCH. With SRB#5 through SRB#31, the RLClayer is operating in the TM and the logical channel is DCCH.

According to the present invention, the user specific C-RNTI can becarried in HS-SCCH by mapping the C-RNTI to H-RNTI in Node B.Alternatively the network can allocate H-RNTI separately to be used alsoin CELL_FACH, CELL/URA_PCH states. During connection setup phase or whenpreviously allocated UE dedicated RNTI is invalid (cell reselection) theUE can use RNTI value broadcasted in system information broadcast (SIB)for receiving RRC message to be used to allocated UE specific RNTI. Asthe UE specific id (UE-id) is carried in HS-SCCH, the PDU structure canbe optimized so that the PDU header does not contain the C-RNTI. Thus, anew PDU structure can be used. The new PDU, according to the presentinvention, is shown in FIG. 3 b. In order to show a MAC multiplexingscheme, according to the present invention, MAC multiplexing structureis also shown alongside the PDU structure.

The present invention can be carried out with a number of improvements.

The first improvement is to remove part of the MAC-c header, without anychanges to MAC-hs header structure. As compared to FIG. 2 b, the MAC-cheader in FIG. 3 b does not contain the TCTF, UE-id type and UE-idfields. As known in the art, TCTF (Target Channel Type Field) is used toidentify the local channel routing for data on FACH and RACH transportchannels, and UE-id type and UE-id fields are used to identify the UE oncommon channels. The UE-id type field indicates whether the subsequentUE-id is of type U-RNTI, C-RNTI or DSCH-RNTI. In the first improvement,the Queue ID, SID, N₁ and F₁ in the MAC-hs PDU, as shown in FIG. 2 b,are kept. Among the parameters of the MAC header (HS-DSCH), Queue ID(Queue identifier) provides identification of the reordering queue inthe receiver in order to support independent buffer handling of databelonging to different reordering queues; SID (Size index identifier)identifies the size of a set of consecutive MAC-d PDUs, N indicates thenumber of consecutive MAC-d PDUs with equal size; and F is a flagindicating whether more fields are present in the MAC-hs header.

The second improvement is to replace the Queue ID with Logical channelID; and replacing SID, N₁ and F₁ with a Length field and an SC field, asshown in FIG. 3 b. Furthermore, the C-RNTI and logical channel ID iscarried from RNC to Node B in FP (Frame Protocol) header which is themapping to the one priority (Node B) and reordering queue (UE) in HSDPAoperation. By including Length field (bytes) and SC field to the MAC-hsinstead of SID, N, and F fields, the segmentation can be done in node Binstead of RLC. The Node B segmentation can take into account theavailable Transport block size in L1.

In addition, the multiplexing structure can be simplified by removingMAC-d multiplexing and MAC-c multiplexing and using MAC-hs multiplexingwhen including data from multiple logical channels from one UE to asingle HS-DSCH TTI. Different UEs can be multiplexed in a single TTI byusing multiple HS-SCCH and Rel5 code multiplexing. With these changesthe MAC PDU structure is identical in CELL_FACH and CELL_DCH state whenHS-DSCH is used for both states (assuming C/T mux is not used inCELL_DCH state). In the MAC PDU structure as shown in FIG. 2 b, the C/Tfield is used to provide identification of the logical channel instancewhen multiple logical channels are carried on the same transportchannel. The C/T mux is used when multiplexing of several dedicatedlogical channels onto one transport channel is used. If the Logicalchannel ID is sent in the MAC-hs header, C/T field is no longer needed.This new Logical channel ID identifies the Logical channel type (e.g.CCCH) as well as the instance of that logical channel type (e.g. DTCH3).

As the MAC-PDU structure remains identical between different CELL_FACHand CELL_DCH states, the UE can receive MAC PDUs correctly in the statetransition procedure from CELL_FACH to CELL_DCH state even if SRNC hasdone CELL_FACH state PDU processing. The only change in UE DL (downlink)reception would be the synchronized UL (uplink) and the normal HS-DPCCHtransmission. Additionally, the H-RNTI value can be potentially changedin reconfiguration, but that is not necessary and H-RNTI used inCELL_FACH state (dedicated for the UE due to mapping from C-RNTI) can beused also in CELL_DCH.

In the case when the UE has no valid C-RNTI and the UE is waiting for acommon control channel (CCCH) message (RRC connection setup, RRCConnection Reject), the UE receives the HS-SCCH with Common H-RNTI(included in SIB or known by other means e.g. hard coded inspecifications) and decodes the MAC-hs PDU. The PDU structure can be thesame as that presented in FIG. 4 a where header structure for SRB#0 forCCCH message is defined.

In the case when the UE has no valid C-RNTI and UE is waiting for a DCCHmessage (Cell update Confirm) with U-RNTI, the UE receives the HS-SCCHwith Common H-RNTI (included in SIB or known by other means e.g. hardcoded in specifications) and decodes the MAC-hs PDU, which indicates theU-RNTI. This MAC-hs PDU structure is the only exceptional format. Theexceptional MAC-hs PDU structure can be identified either from thelogical channel ID or the use of Common H-RNTI or combined usage ofboth. This exception MAC-hs PDU has two different MAC-hs headers asshown in FIGS. 4 b and 4 c.

In the case involving multimedia broadcast/multicast service (MBMS) thatuses logical channels such as MTCH (MBMS point-to-multipoint trafficchannel), MSCH (MBMS point-to-multipoint scheduling channel), and MCCH(MBMS point-to-multipoint control channel) for point-to-multipoint(p-t-m) transmission, and when the UE is receiving a MCCH or MTCH mappedon HSDPA, the UE receives the HS-SCCH either with Common H-RNTI(included in SIB for MCCH) or MBMS service specific H-RNTI indicated inMCCH, and it decodes the MAC-hs PDU. The PDU structure can be the same.The MAC-hs header for this case is shown in FIG. 4 d.

In that case that the UE is receiving a BCCH or PCCH mapped on HSDPA,the UE receives the HS-SCCH with Common H-RNTI, included in SIB, and itdecodes the MAC-hs PDU. The PDU structure can be the same, as presentedin FIG. 4 e.

In summary, in the method for improving the PDU structure, according tothe present invention, the first change is to remove TCTF, UE-id typeand UE-id fields in the MAC-hs header. The second change is to replacethe Queue ID field with Logical channel ID field, replacing the SID, N1and F1 fields with Length field and SC field. The third improvement isto remove the MAC-d and MAC-c multiplexing.

Implementation

FIGS. 3 a and 3 b present the multiplexing and PDU structure for HS-FACHoperation, according to the present invention. The Logical channel ID isused to separate different logical channels and logical channel typesand reordering queue. TSN is used for MAC-hs reordering after HARQretransmissions as in Rel5, but the reordering is identified implicitlyfrom the logical channel, and no separate reordering queue ID field isneeded. Length indicates the length of the MAC-hs SDU (service dataunit) in bytes. By repeating the header, data also from other logicalchannels can be multiplexed in the same transport block, as the UEcompares the amount of data indicated in Length field and the transportblock size.

FIGS. 4 a to 4 e illustrate the MAC-hs PDU structures for varioussignaling radio bearers (SRBs) and radio bearers (RBs). FIG. 4 a showsthe MAC-hs header for a signaling radio bearer (SRB #0) and the logicalchannel used being CCCH (common control channel). FIG. 4 b shows theMAC-hs header for a signaling radio bearer (SRB#1) and the logicalchannel used being DCCH (dedicated control channel) with U-RNTH. FIG. 4c shows the MAC-hs header for the signaling radio bearers #2-4 and RBs(DCCH and DTCH messages) with UE dedicated H-RNTI in CELL_FACH orCELL_DCH state. FIG. 4 d shows the MAC-hs header for the signaling radiobearers #2-4 with logical channels, such as MTCH, MSCH and MCCH, forMBMS point-to-multipoint transmission. FIG. 4 e shows the MAC-hs headerfor signaling radio bearers #2-4 with logical channels such as BCCH andPCCH carried over HSDPA.

FIGS. 5 a and 5 b present the full header structures including AMD-RLCand MAC-hs headers. The length of the RLC header is 2 octets and nolength indicators are used. AMD PDU (Acknowledged Mode Data PDU) is usedto convey sequentially numbered PDUs containing RLC SDU data. RLC usesAMD PDUs when it is configured for transferring acknowledged data.

The RLC AMD PDU structure, according to the present invention, supportssimple segmentation with a 1 or 2-bit last segment flag (L) (a one-bitflag would be enough, but with two bits the beginning of the SDU canalso be indicated). This is sufficient when concatenation at an RLClayer is not supported and if all the RLC PDUs are received correctly.If the PDU with last segment bit set is lost, the SC field is used toindicate the first segment of the SDU, 2-n^(th) (=middle) segment of theSDU and last segment of the SDU, avoiding the problem of one missed RLCPDU. The P field contains a polling bit indicating whether a statusreport is required. The D/C field indicates whether the PDU is a controlPDU or an AM PDU.

If the segmentation (at least partly) is moved from RLC to MAC, thenMAC-hs has to support it in DL. The priority queue id (Queue ID) and C/Tfield are replaced by the Logical channel ID assuming that logicalchannel number is transferred in FP header in a similar manner as C-RNTIis also transferred in FP header. C-RNTI is transmitted over the air inHS-SCCH.

The Length field gives the length of the segment of MAC-d PDU (orequivalently RLC PDU assuming that MAC-d does not add any header) inbytes. SC field tells whether the segment is a complete SDU (=00), firstsegment (=01), last segment (=10) or a middle segment (=11), forexample. Such an AMD PDU is shown in FIG. 5 a.

Concatenation of MAC-d PDU segments of different MAC-d PDUs of the sameor different logical channel is possible simply by repeating the threebytes header for each segment. The additional header can be either atthe beginning after the first header or after the first payload togetherwith the payload of the next segment. The existence of the additionalheader can be inferred by comparing the signaled TB size and the lengthfield of the first header. If the smallest possible TB size is so large(more than 3 bytes larger than the MAC-hs header+payload) that anadditional header fits in, then, e.g., the length field can be set tozero. Thus there is no need to explicitly indicate the number ofsegments/headers, as shown in FIG. 5 b.

If the 15 different logical channel IDs are not sufficient, then either5, 6 or 7 bits can be reserved for logical channel ID and the MAC-hsheader size is extended to 4 octets to keep the octet align headerstructures. In this case, 7, 6, or 5 bits are reserved for future use orthey can contain the length of the next complete SDU, which isconcatenated from the same logical channel, e.g. TCP ACK. Alternatively,it is possible that Status PDU be piggybacked to MAC-hs PDU without thefull 4-octet PDU structure. Fixed values can be defined for the reservedbits to indicate these optimizations in MAC-hs header. It is alsopossible that the field be used for MAC-hs control messages between NodeB and UE.

The present invention has the following advantages:

-   -   1. L2 header overhead is reduced as C-RNTI is not needed in each        PDU.    -   2. MAC multiplexing structure is simplified as only MAC-hs        multiplexing is used.    -   3. MAC-hs reordering is done separately for each logical        channel, removing the head of the queue blocking problem.    -   4. DCCH, DTCH can use identical L2 protocol header structure in        CELL_DCH and CELL_FACH state.    -   5. Due to the identical header structure, the UE can receive the        PDU correctly in CELL_FACH to CELL_DCH state transition and the        only difference is the change of the uplink synchronization        status and the potential usage of new H-RNTI.    -   6. Protocol architecture can be the same for CELL_FACH and        CELL_DCH, i.e. if segmentation is moved from RLC to MAC-hs, the        segmentation is done also in MAC-hs even if UE is in CELL_FACH        state, and therefore segmentation can be performed based on        physical layer requirement and data loss is minimized.    -   7. All PDUs are octet aligned, making the data processing        simpler in UE and in UTRAN.    -   8. The utilization of RLC Length indicators can be avoided and        thus the length indicator does not need to be configured either        to 7 bit with maximum RLC PDU size of 127 octets or to 15 bit        introducing always 2 octet overhead for small RLC SDUs.        Additionally, the complexity of supporting simultaneously both 7        bit and 15 Length indicators can be avoided, when supporting        flexible RLC PDU size between 40 bytes to 1500 bytes.        Furthermore, the RLC SDU size of 40 bytes (TCP ACK) can be        fitted to RLC PDU size of 336 bits, de-facto implementation of        RLC PDU size in UL.    -   9. Only RLC concatenation (and partly RLC segmentation) is        removed and other RLC functions do not change except for the        piggybacked status, which is no longer used. Status PDUs are        sent as separate RLC PDUs. A solution is presented for        piggybacking the status PDU at MAC-hs level (with the four octet        MAC-hs header).    -   10. Sequence number space problems can be avoided and the RLC        processing load is decreased as bigger RLC PDUs sizes are used.

However, in order to fully utilize the MAC-hs PDU according to thepresent invention, a new MAC-hs structure must be defined and thepiggybacked status is no longer available in RLC (but can be used atMAC-hs level instead).

The present invention is mainly described with HS-FACH (mapping data andsignaling of the UE in CELL_FACH state on HS-DSCH) as an example. Itshould be noted as explicitly shown in FIGS. 4 a to 4 e that the MAC-hsand RLC PDU structures, according to the present invention, areapplicable for other channels mapped on HSDPA in any RRC state of theUE.

UTRAN has been used as an example in this application. It should benoted that the same principles of RLC PDU structures and RLC functions,MAC-hs PDU structures and MAC-hs functions, etc. disclosed herein can beapplied to other systems as well. One particular example is the longterm evolution (LTE) of UTRAN currently being specified in 3GPP.

The present invention includes the following features:

-   1) for UE there can be C-RNTI allocated:    -   1.1 for both UL (uplink) and DL (downlink) purposes ->C-RNTI is        used for UL, and it is also mapped to H-RNTI in HS-SCCH;    -   1.2 only for UL purposes and H-RNTI is allocated for DL;    -   1.3H-RNTI can have same value in CELL_DCH state as C_RNTI        CELL_FACH ->So no change of UE id value is used in HS-SCCH        during state transition;-   2) UE in CELL_DCH state is able to receive data that is processed in    RNC and Node B in CELL_FACH (common) state.-   3) Regarding the common state, at least one of the following should    be true:    -   3.1 No UE context established to Node B by RNC or any other        network element in the network, e.g., AGW (Access Gateway) in        LTE;    -   3.2 No UE id verification done for Node B by RNC or any other        network element in the network, e.g., AGW in LTE;    -   3.3 No network controlled mobility. Examples are CELL_FACH.

The above definition does not restrict the implementations where Node Band RNC are co-located in the same physical network element supportingfunctions of Node B and RNC. Nor implementations where Node B and AGWare co-located in same physical NW element supporting functions of NodeB and AGW.

In the present invention, both Logical Channel (type and instance) androuting (re-ordering queue) are identified by the new Logical channel IDfield. Idle mode is also used in RRC connection setup in addition toCELL_FACH and CELL_DCH state. The inventive features also include: samePDU structure is used in multiple RRC states; MAC-hs is onlymultiplexing layer for HS-DSCH transport channel.

Thus the present invention provides a method and structure forcommunicating a protocol data unit to/from a user equipment over alogical channel in a radio access network, the protocol data unitcomprising a plurality of fields in a header section. The methodcomprises indicating the UE identity in out-of-band signaling, andidentifying the logical channel and its routing in the protocol dataunit in a common state. With the method and structure, according to thepresent invention, the receiver is able to know the format of the PDU bythe out-of-band signaling of the receiver identity (i.e., the H-RNTIused can also tell the UE the format of the PDU to use for decoding).Furthermore, depending on the state of the receiver, the receiver knowswhich identity should be used in the out-of-band signaling.Alternatively, depending on the ID detected, the receiver knows thetransmitter has moved from one state to another and the receiver movesthe state as well. It is possible to use both identities for a certainperiod of time so as to synchronize the states more tightly. Moreover,the Node B can detect the state of the UE and which identity is beingused by the UL activity (starting of ACK/NACKs will tell the Node B thatthe UE is using a different H-RNTI).

According to the present invention, the method further comprisesindicating the field indicative of the logical channel being carriedwithout indicating separately the logical channel type and/or logicalchannel instance, and not indicating the UE identity or UE Id-type inthe protocol data unit.

The method also replaces the field indicative of reordering queue in thereceiver by a field indicative of identity of the logical channel andreplaces one or more of the fields in the header section indicative ofnumber or size of one or more subsequent protocol data units by a fieldindicative of a length of the service data unit.

The method also comprises indicating that included data is firstsegment, mid segment or last segment of the SDU. When the protocol dataunit is used in a high-speed medium access control layer, the protocoldata unit is used to transfer data and signaling to the UE in Idle,CELL_FACH or CELL_DCH state and the protocol data unit as singlemultiplexing layer for multiplexing different logical channels totransport channel (High Speed Downlink Shared Channel).

One improvement regarding the PDU structure change, according to thepresent invention, is to allow continuous reception (without breaks inconsecutive TTIs) of the HS-DSCH downlink channel during the statetransition from CELL_FACH or CELL_PCH or URA_PCH (for UTRAN RegistrationArea) to CELL_DCH or vice versa.

One improvement regarding the PDU structure change, according to thepresent invention, is to allow HS-DSCH HARQ retransmissions to continueduring the state transition from CELL_FACH to CELL_DCH or vice versa.This is possible as PDU structure in both states is identical and, fromreceiver point of view, there is no difference if some first HARQtransmission occurred in a different state than the last HARQtransmission when the PDU were able to be decoded correctly.

One improvement regarding the PDU structure change, according to thepresent invention, is to allow a variable MAC-hs SDU size by utilizingthe length field.

One improvement regarding the PDU structure change, according to thepresent invention, MAC-hs segmentation and concatenation in CELL_DCH andCELL_FACH states. The segmentation is achieved by utilizing the lengthand SC fields and concatenation is achieved by repeating the headerfields.

One improvement regarding the PDU structure change, according to thepresent invention, is to avoid length indicators in RLC to indicate SDUborders. This is achieved by using last field in the RLC header toindicate the end of the SDU. Thus, the Length field as shown in FIG. 3 bis not used in order to allow the RLC to be flexible. The RLC header hasa last segment flag (L) to indicate the last segment, a polling bit (P)to indicate a status report is required, and a D/C field to indicatewhether the PDU is a control PDU or an AM PDU. It should be also notedthat actual order of the different fields in MAC-hs protocol header notessential for this invention.

One improvement regarding the PDU structure change, according to thepresent invention, is to reduce the overall L2 overhead introduced byRLC and MAC layers in CELL_FACH, CELL_PCH, URA_PCH and CELL_DCH state.

The PDU, according to various embodiments of the present invention, isused for communications between various network components in a radioaccess network. The PDU can be communicated between a user equipment(UE) and another network component. As shown in FIG. 6 a, the othernetwork component can be a serving radio network controller (S-RNC), acontrolling radio network controller (C-RNC) or a Node B. The PDU canalso be communicated between Node B and S-NRC or C-RNC, as illustratedin FIG. 6 b. The PDU can also be communicated between S-NRC and C-RNC,as illustrated in FIG. 6 c. At least one of the network components, suchas S-RNC, has an apparatus for handling the PDU for communicating toanother network component. As shown in FIG. 7 a, the apparatus comprisesa module for segmenting the header of a PDU, and indicating the identityof a UE in the header for out-of-band signaling, or indicating theidentity of a logic channel over which the PDU is communicated. Theapparatus also has a transmitter to convey the PDU from one networkcomponent to another. In the receiving end of the PDU, as shown in FIG.7 b, the apparatus has a module configured for receiving the PDU and forobtaining the identity of the PDU sender or the identity of the logicalchannel over which the PDU is communicated. Based on the identity, theinformation processor identify the format of the PUD, for example. Theapparatus may also have a module for enabling a HARQ soft combiningduring a state transition or during a uplink synchronization process.

In summary, the present invention provides a method, comprising:

indicating identity of a first network component in a radio accessnetwork in out-of-band signaling, the first network component configuredfor communicating a protocol data to a second network component over alogical channel in the radio access network, and

identifying the logical channel and routing of the logical channel inthe protocol data unit.

The logical channel and the routing are identified in the protocol dataunit in common state or in dedicated state.

The first network component can be a user equipment device configuredfor communicating the protocol data unit in the radio access network,and the protocol data unit includes a common control channel (CCCH)message when the UE identity is transmitted by dedicated RRC signaling,i.e., out-of-band signaling in radio resource controller signaling.

The second network component comprises a serving radio networkcontroller, and wherein the message is provided to the serving radionetwork controller configured for allocating the logical channel and therouting.

The protocol data unit may include dedicated control channel data forallocating the identity of the user equipment device, or dedicatedtraffic channel data for the user equipment device. In other words, ifUE identity is UE specific and is uniquely allocated for the UE, theprotocol data unit contains unique data for that UE—data from DCCH orDTCH.

The identity of the user equipment device is BCCH specific for broadcastcontrol channel (BCCH) transmission.

The identity of the user equipment device can be indicated in a mediumaccess control layer or in radio resource controller layer.

Furthermore, the logical channel has an identity and the protocol dataunit comprises a plurality of fields in a header section, and one of thefields comprises information indicative of the identity of the logicalchannel, including logical channel type and instance.

When the second network component comprises a receiver in the radioaccess network and the protocol data unit is communicated to thereceiver in a high-speed medium access control (MAC-hs) or enhancedhigh-speed medium access control (MAC-ehs) layer, the protocol data unitcomprises a header section including a field indicative of reorderingqueue in the receiver, and wherein the logical channel has an identity,and the reordering queue can be indicated by the identity of the logicalchannel.

When the protocol data unit is communicated in a high-speed mediumaccess control layer, the protocol data unit comprising a service dataunit and a header section, the header section comprising one or morefields indicative of number or size of one or more subsequent protocoldata units, the one or more of the fields in the header section can bereplaced by a field indicative of a length of the service data unit.

When the protocol data unit is communicated in a high-speed mediumaccess control layer, the protocol data unit is configured fortransferring data and for signaling to the user equipment device in oneor more of the idle state, a forward access channel (CELL_FACH) stateand a dedicated channel (CELL_DCH) state.

According to one embodiment of the present invention, the protocol dataunit is communicated in a high-speed medium access control layer, andthe medium access control layer is configured for use as a singlemultiplexing layer for multiplexing different logical channels to atransport channel (High Speed Downlink Shared Channel).

According to another embodiment of the present invention, when theprotocol data unit is communicated to a receiver in the radio accessnetwork, the protocol data unit having a format, and the receiver has areceiver identity, wherein the receiver is configured to recognize theformat by the out-of-band signaling of the receiver identity.

According to a different embodiment of the present invention, the methodfor communicating a protocol data unit, the protocol data unitcomprising a service data unit and a header section, comprisesindicating in the header section whether one or more service data unitsare present in the protocol data unit by segmentation control field.

When the protocol data unit is communicated in a high-speed mediumaccess control (MAC-hs) layer, and wherein said one or more service dataunits comprise a plurality of segments, the method further comprisesindicating the segments of said one or more MAC-hs service data units inthe header section of the protocol data unit.

When the protocol data unit is communicated in a radio link controlprotocol (RLC), and said one or more service data units comprise aplurality of segments, the method further comprises indicating thesegments of said one or more RLC service data units in the headersection of the protocol data unit. The one or more protocol data unitscomprise a first segment, a last segment and a mid segment locatedbetween the first and last segments. The one or more protocol data unitsmay comprise indication of a last segment of the service data unit.

In yet another embodiment of the present invention, the protocol dataunit having a format, and wherein at least the first network componentis configured for changing from one state to another in a statetransition, said method comprises receiving during the state transitionwith same PDU format processed by the first network component indifferent state than the second network component and enablinghigh-speed downlink shared channel (HS-DSCH) hybrid automatic repeatrequest (HARQ) soft combining during the state transition

In a different embodiment of the present invention, the protocol dataunit having a format, and method comprises receiving during uplinksynchronization process with same PDU format processed by the firstnetwork component in different uplink synchronization status than thesecond network component and enabling high-speed downlink shared channel(HS-DSCH) hybrid automatic repeat request (HARQ) soft combining duringthe uplink synchronization process

According to one embodiment of the present invention, the radio accessnetwork comprises an apparatus, which comprises:

a receiving module for receiving an identity of a first networkcomponent in out-of-band signaling, wherein the first network componentis configured for communicating a protocol data unit to a secondprotocol network component in a radio access network; and

a determining module for determining a format of the protocol data unitbased on the identity.

According to another embodiment of the present invention, the radioaccess network comprises an apparatus, which comprises:

a receiving module for receiving an identity of the logical channel in aradio access network, wherein the radio access network comprising afirst network component and a second network component, first networkcomponent configured for communicating a protocol data unit to a secondprotocol network component; and

a determining module for determining a format of the protocol data unitbased on the identity.

According to yet another embodiment of the present invention, the radioaccess network comprises an apparatus for use in a radio access networkcomprising a first network component and a second network component, thefirst network component and the second network component configured forcommunicating a protocol data unit (PDU) having a format, and wherein atleast the first network component is configured for changing from onestate to another in a state transition. The apparatus comprises:

a receiving module configured for receiving the protocol data unitduring the state transition with same PDU format processed by the firstnetwork component in different state than the second network componentand

an enabling module configured for enabling high-speed downlink sharedchannel (HS-DSCH) hybrid automatic repeat request (HARQ) soft combiningduring the state transition

According to a different embodiment of the present invention, the radioaccess network comprises an apparatus, the radio access networkcomprising a first network component and a second network component, thefirst network component and the second network component configured forcommunicating a protocol data unit (PDU) having a format. The apparatuscomprises:

a receiving module configured for receiving the protocol data unitduring uplink synchronization process with same PDU format processed bythe first network component in different uplink synchronization statusthan the second network component and

an enabling module configured for enabling high-speed downlink sharedchannel (HS-DSCH) hybrid automatic repeat request (HARQ) soft combiningduring the uplink synchronization process.

According to another embodiment of the present invention, an apparatusfor use in a radio access network comprising a first network componentand a second network component, the first network component and thesecond network component configured for communicating a protocol dataunit (PDU), the PDU has a header section. The apparatus comprises:

a module for segmenting the header section into plurality of fieldsincluding a control field, and

a module for indicating in the control field whether one or more servicedata units are present in the PDU.

In addition, the method of communicating a PDU may have the followingfeatures:

The identity of the user equipment device is associated with the logicalchannel in the out-of-band signaling.

When the protocol data unit is communicated in a medium access control(MAC-hs) layer, and protocol data unit comprising a header section, saidmethod comprising:

indicating in the header section a size of a service data unit fortransferring user data.

The user data comprises a plurality of data segments, the method furthercomprises indicating in the header section whether one or more datasegments are present in the service data unit.

The identity of the user equipment device is provided in a message fromsaid user equipment device requesting a radio resource controllerconnection, and the message is provided to a serving radio networkcontroller in the radio access network, and the serving radio network isconfigured for allocating the logical channel and the routing inresponse to the message;

assigning a radio network temporary identity for the connection; and

associating the identity of the user equipment device with the radionetwork temporary identity.

When the serving radio network controller is configured for sending aconnection set-up message to the user equipment device confirmingestablishment of the connection, the user equipment device is configuredto enter a dedicated channel state (CELL_DCH) and a forward accesschannel state (CELL_FACH), and wherein the protocol data unit used inthe dedicated channel state and the protocol data unit used in theforward access channel state are identical.

When the user equipment device can be configured to enter an idle stateand a terrestrial radio access (UTRAN) connection state, the methodcomprises using the protocol data unit for transferring data andsignaling to the user equipment device in the idle or the terrestrialradio access state.

When the protocol data unit is communicated in a high-speed mediumaccess control layer, the medium access control layer configured for useas a single multiplexing layer for multiplexing different logicalchannels to a transport channel, and the serving radio networkcontroller is configured for sending a connection set-up message to theuser equipment device indicating establishment of the connection, andthe user equipment device is configured to enter a dedicated channelstate (CELL_DCH) and a forward access channel state (CELL_FACH), themethod further comprises

using the protocol data unit in both the dedicated channel state and theforward access channel state when high-speed downlink shared channel(HS_DSCH) reception is enabled in the dedicated channel state and in theforward access channel state. When the user equipment device is alsoconfigured to enter a paging channel (CELL_PCH) state, the methodfurther comprises using the protocol data unit in a transition from theforward access channel state or the paging state to the dedicatedchannel state when high-speed downlink shared channel (HS_DSCH)reception is enabled in the dedicated channel state, the paging stateand the forward access channel state so as to maintain a continuousreception in consecutive transmission time intervals. The protocol dataunit can be used in a transition between the forward access channelstate and the dedicated channel state during high-speed downlink sharedchannel (HS DSCH) hybrid automatic repeat request (HARQ)retransmissions.

Although the present invention has been described with respect to one ormore embodiments thereof, it will be understood by those skilled in theart that the foregoing and various other changes, omissions anddeviations in the form and detail thereof may be made without departingfrom the scope of this invention.

1. A method, comprising: indicating identity of a first networkcomponent in a radio access network in out-of-band signaling, the firstnetwork component configured for communicating a protocol data to asecond network component over a logical channel in the radio accessnetwork, and identifying the logical channel and routing of the logicalchannel in the protocol data unit.
 2. The method of claim 1, wherein thelogical channel and the routing are identified in the protocol data unitin common state.
 3. The method of claim 1, wherein the logical channeland the routing are identified in the protocol data unit in dedicatedstate.
 4. The method of claim 1, wherein the first network componentcomprises a user equipment device configured for communicating theprotocol data unit in the radio access network.
 5. The method of claim4, wherein the protocol data unit comprises a common control channelmessage, and wherein said out-of-band signaling is carried out in radioresource controller signaling.
 6. The method of claim 5, wherein thesecond network component comprises a serving radio network controller,and wherein the message is provided to the serving radio networkcontroller configured for allocating the logical channel and therouting.
 7. The method of claim 4, wherein the protocol data unitcomprises dedicated control channel data for allocating the identity ofthe user equipment device.
 8. The method of claim 4, wherein theidentity of the user equipment device is specific for broadcast controlchannel transmission.
 9. The method of claim 4, wherein the identity ofthe user equipment device is indicated in a medium access control layeror a in radio resource controller layer.
 10. The method of claim 4,wherein the protocol data unit comprises dedicated traffic channel datafor the user equipment device.
 11. The method of claim 4, wherein thelogical channel has an identity and the protocol data unit comprises aplurality of fields in a header section, wherein one of the fieldscomprises information indicative of the identity of the logical channel,including logical channel type and instance.
 12. The method of claim 4,wherein the second network component comprises a receiver in the radioaccess network and the protocol data unit is communicated to thereceiver in a high-speed medium access control (MAC-hs) or enhancedhigh-speed medium access control (MAC-ehs) layer, the protocol data unitcomprising a header section including a field indicative of reorderingqueue in the receiver, and wherein the logical channel has an identity,said method further comprising: indicating the reordering queue by theidentity of the logical channel.
 13. The method of claim 4, wherein theprotocol data unit is communicated in a high-speed medium access controllayer, the protocol data unit comprising a service data unit and aheader section, the header section comprising one or more fieldsindicative of number or size of one or more subsequent protocol dataunits, said method further comprising: replacing said one or more of thefields in the header section by a field indicative of a length of theservice data unit.
 14. The method of claim 4, wherein the protocol dataunit is communicated in a high-speed medium access control layer, andwherein the protocol data unit is configured for transferring data andfor signaling to the user equipment device in one or more of the idlestate, a forward access channel (CELL_FACH) state and a dedicatedchannel (CELL_DCH) state.
 15. The method of claim 1, wherein theprotocol data unit is communicated in a high-speed medium access controllayer, the medium access control layer configured for use as a singlemultiplexing layer for multiplexing different logical channels to atransport channel (High Speed Downlink Shared Channel).
 16. The methodof claim 1, wherein the protocol data unit is communicated to a receiverin the radio access network, the protocol data unit having a format, andthe receiver has a receiver identity, wherein the receiver is configuredto recognize the format by the out-of-band signaling of the receiveridentity.
 17. The method for communicating a protocol data unit, theprotocol data unit comprising a service data unit and a header section,said method comprising: indicating in the header section whether one ormore service data units are present in the protocol data unit bysegmentation control field.
 18. The method of claim 17, wherein theprotocol data unit is communicated in a high-speed medium access control(MAC-hs) layer, and wherein said one or more service data units comprisea plurality of segments, said method further comprising: indicating thesegments of said one or more MAC-hs service data units in the headersection of the protocol data unit.
 19. The method of claim 17, whereinthe protocol data unit is communicated in a radio link control protocol(RLC), and wherein said one or more service data units comprise aplurality of segments, said method further comprising: indicating thesegments of said one or more RLC service data units in the headersection of the protocol data unit.
 20. The method of claim 17, whereinsaid one or more protocol data units comprise a first segment, a lastsegment and a mid segment located between the first and last segments.21. The method of claim 17, wherein said one or more protocol data unitscomprise indication of a last segment of the service data unit.
 22. Amethod for communicating a protocol data unit between a first networkcomponent and a second network component in a radio access network, theprotocol data unit having a format, and wherein at least the firstnetwork component is configured for changing from one state to anotherin a state transition, said method comprising: receiving during thestate transition with same PDU format processed by the first networkcomponent in different state than the second network component andenabling high-speed downlink shared channel (HS-DSCH) hybrid automaticrepeat request (HARQ) soft combining during the state transition
 23. Amethod for communicating a protocol data unit between a first networkcomponent and a second network component in a radio access network, theprotocol data unit having a format, said method comprising: receivingduring uplink synchronization process with same PDU format processed bythe first network component in different uplink synchronization statusthan the second network component and enabling high-speed downlinkshared channel (HS-DSCH) hybrid automatic repeat request (HARQ) softcombining during the uplink synchronization process
 24. An apparatus,comprising: a receiving module for receiving an identity of a firstnetwork component in out-of-band signaling, wherein the first networkcomponent is configured for communicating a protocol data unit to asecond protocol network component in a radio access network; and adetermining module for determining a format of the protocol data unitbased on the identity.
 25. An apparatus, comprising: a receiving modulefor receiving an identity of the logical channel in a radio accessnetwork, wherein the radio access network comprising a first networkcomponent and a second network component, first network componentconfigured for communicating a protocol data unit to a second protocolnetwork component; and a determining module for determining a format ofthe protocol data unit based on the identity.
 26. An apparatus for usein a radio access network comprising a first network component and asecond network component, the first network component and the secondnetwork component configured for communicating a protocol data unit(PDU) having a format, and wherein at least the first network componentis configured for changing from one state to another in a statetransition, said apparatus comprising: a receiving module configured forreceiving the protocol data unit during the state transition with samePDU format processed by the first network component in different statethan the second network component and an enabling module configured forenabling high-speed downlink shared channel (HS-DSCH) hybrid automaticrepeat request (HARQ) soft combining during the state transition
 27. Anapparatus for use in a radio access network comprising a first networkcomponent and a second network component, the first network componentand the second network component configured for communicating a protocoldata unit (PDU) having a format, said apparatus comprising: a receivingmodule configured for receiving the protocol data unit during uplinksynchronization process with same PDU format processed by the firstnetwork component in different uplink synchronization status than thesecond network component and an enabling module configured for enablinghigh-speed downlink shared channel (HS-DSCH) hybrid automatic repeatrequest (HARQ) soft combining during the uplink synchronization process.28. An apparatus for use in a radio access network comprising a firstnetwork component and a second network component, the first networkcomponent and the second network component configured for communicatinga protocol data unit (PDU), the PDU has a header section, said apparatuscomprising: a module for segmenting the header section into plurality offields including a control field, and a module for indicating in thecontrol field whether one or more service data units are present in thePDU.